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Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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404 FXUS64 KMRX 291903 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 303 PM EDT Sat Jun 29 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Sunday) Issued at 254 PM EDT Sat Jun 29 2024 Key Messages: 1. Isolated to scattered showers and storms through this evening. No severe weather expected. 2. Scattered to widespread showers and storms expected tomorrow. A few strong storms are probable. An isolated severe storm is possible. Discussion: Not much change for tonight or tomorrow compared to the last forecast. We remain in quasi-zonal flow out ahead of an approaching cold front. This has allowed diurnal showers and storms to develop across the area this afternoon. This activity will decrease in coverage as we lose daytime heating but a few isolated showers and storms will likely linger through the night. No severe weather is expected, but an isolated strong storm is possible. Tomorrow, showers and storms increase in coverage as a cold front advances toward the area. The highest coverage will be during the afternoon hours, during peak heating. HREF ensemble probabilities show a 50 to 60% chance for SBCAPE of 2000 J/kg by tomorrow afternoon. 0-6km shear remains weak and will generally be 20kts or less. Because of the weak shear and moderate instability, a few strong storms are probable. While most storms will remain below severe limits, an isolated severe thunderstorm is possible. The main threats will be damaging wind gusts. This thinking still aligns with SPC`s Day 2 Marginal Risk. Showers and storms will decrease in coverage by Sunday evening as we lose heating. The cold front will pass through sometime overnight. && .LONG TERM... (Sunday night through next Saturday) Issued at 254 PM EDT Sat Jun 29 2024 Key Messages: 1. Brief cooler temperatures Monday before a warming trend quickly returns for the remainder of the week. 2. Mostly dry through Wednesday, albeit a few isolated showers or storm possible Wednesday afternoon, with daily chances for showers and a few storms late week and into the weekend. Discussion: A post-frontal air mass will result in a return of cooler, more seasonable temperatures Monday afternoon. Conditions will remain dry as high pressure and associated subsidence take control. The seasonable temperatures will be short-lived however, as upper troughing atop the eastern CONUS coastline lifts north and east Tuesday, leading to upper level height increases locally. Temperatures slightly above normal are then expected to persist through the remainder of the extended period. By Wednesday afternoon, shortwave energy traversing over the Great Lakes region will flatten aforementioned ridging. Weakening subsidence will bring a return to isolated diurnal showers and storms favoring high elevations. Daily chances of showers and storms are expected to continue into the weekend, though there becomes more uncertainty with expected coverage towards the end of the period. The uncertainty is linked to a surface boundary and how far south it drops before stalling out. Recent GFS runs suggest limited coverage Thursday and Friday as the boundary stalls well to our north, where as ECMWF suggest greater coverage of activity. A more potent shortwave is expected to kick the boundary through by the weekend, with potential for a brief cooler period behind the front. && .AVIATION... (18Z TAFS) Issued at 112 PM EDT Sat Jun 29 2024 Forecasting VFR through the period at all sites. However, brief MVFR conditions could occur if any shower or storm passes over a terminal. Isolated showers and storms are expected through this evening. Additional showers and storms expected toward the end of the period. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 75 94 70 89 / 20 70 20 0 Knoxville McGhee Tyson Airport, TN 75 90 66 85 / 30 70 40 0 Oak Ridge, TN 74 90 63 84 / 30 80 40 0 Tri Cities Airport, TN 72 86 62 82 / 40 80 50 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... LONG TERM....KRS AVIATION...